1. Field of the Invention
Exemplary embodiments of the present invention relate to a multi-point support chuck for use in an exposure apparatus or an optical inspection apparatus.
2. Description of the Background
To adjust a chuck on a stage to a height of focus of an optical projection system, a test exposure may be performed in which a plate placed on the chuck is exposed while varying the height of the chuck. Based on the test results, a height of the chuck representing the highest resolution may be determined, and the determined height may be set to a reference height of the chuck.
Upon adjusting a position of the chuck to the reference height and exposing the plate on the chuck, auto focusing is performed while the stage is located at a certain position within an exposure region. If the reference height of the chuck differs from a height required for accurate focusing, the position of the chuck may be adjusted above or below the reference height, so as to accurately locate the plate on the chuck at the focus point of the optical projection system.
In the case of an exposure apparatus or an optical inspection apparatus, Depth of Focus (DOF) is an important tuning parameter. DOF of the exposure apparatus refers to a depth of focus in a longitudinal direction of an optical system to enable a pattern to be normally exposed onto a plate. DOF of the optical inspection apparatus refers to a depth of focus of an image capture device (e.g., a camera). A plate in the exposure apparatus or the optical inspection apparatus may be located within a predetermined DOF range.
With recent increases in the size of Liquid Crystal Displays (LCDs), the plate size used in manufacturing an LCD panel is increasing, which, in turn, is causing an increase in the size of a chuck on which the plate is placed during manufacture. However, as the size of the chuck increases, it may be difficult to ensure flatness or balance of the chuck due to, for example, buckling of the chuck by a weight of the chuck or limited mechanical accuracy of the chuck. If the plate placed on the chuck is exposed in a state in which the chuck fails to exhibit flatness or balance, locating the entire plate within a DOF range may be difficult, which increases the likelihood of exposure failure.
Although most exposure apparatuses are provided with an auto-focus module, the auto-focus module has limited abilities, and therefore, the chuck used to support the plate may require an extremely high level of flatness. In addition, since the chuck may be leveled with respect to a focus sensor, it may be necessary to minimize change of the focus throughout the plate.